Not sure that's true.tamanaco...you're problem most likely is that you have a custom recovery on your N7. An OTA will not be successfully installed with a custom recovery present. You have a couple of options...I prefer option 2, but here goes: 1) Use the Toolkit to restore the "stock recovery", download and install Voodoo Rootkeeper, backup root, then temp unroot and take the OTA update to 4.2.1. After the OTA has finished you can restore root with Voodoo Rootkeeper. Option 2...using the Toolkit restore "stock recover", unroot and take the OTA. After OTA has finished use the Toolkit to root and install a custom recovery.
I have TWRP installed and the OTA went on OK on both my Nexus 7 and Nexus 10.
I had to use VOODOO ROOTKEEPER to restore root and re-flash TWRP but all working OK.
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